U.S. patent application number 12/732155 was filed with the patent office on 2010-11-11 for percutaneous bone conduction implant.
This patent application is currently assigned to Cohlear Limited. Invention is credited to Marcus Andersson.
Application Number | 20100286776 12/732155 |
Document ID | / |
Family ID | 42664025 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100286776 |
Kind Code |
A1 |
Andersson; Marcus |
November 11, 2010 |
PERCUTANEOUS BONE CONDUCTION IMPLANT
Abstract
One embodiment relates to a percutaneous bone conduction
implant. The implant includes a fixture configured to be anchored
in the recipient's skull, and a skin-penetrating abutment
configured to interface with the fixture and to permit the abutment
to be removably attached to the fixture to form a fixture-abutment
assembly. In an embodiment, at least one anti-microbial surface
forms one or more surfaces of the formed fixture-abutment assembly
located in an interior of the formed fixture-abutment assembly when
the fixture is removably attached to the abutment with an abutment
screw. The interior is substantially isolated from a surrounding
environment of the fixture-abutment assembly.
Inventors: |
Andersson; Marcus;
(Goteborg, SE) |
Correspondence
Address: |
KILPATRICK STOCKTON LLP
1100 Peachtree Street, Suite 2800
ATLANTA
GA
30309
US
|
Assignee: |
Cohlear Limited
Lane Cove
AU
|
Family ID: |
42664025 |
Appl. No.: |
12/732155 |
Filed: |
March 25, 2010 |
Current U.S.
Class: |
623/16.11 ;
606/301 |
Current CPC
Class: |
H04R 25/606 20130101;
A61L 2300/406 20130101; A61L 2300/404 20130101; A61L 27/54
20130101; A61L 2300/102 20130101; A61L 2300/104 20130101; A61L
2430/14 20130101; A61L 2300/45 20130101 |
Class at
Publication: |
623/16.11 ;
606/301 |
International
Class: |
A61F 2/28 20060101
A61F002/28; A61B 17/86 20060101 A61B017/86 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2009 |
DE |
102009014771.3 |
Claims
1. A percutaneous bone conduction implant, comprising: a fixture
configured to be anchored in the recipient's skull; and a
skin-penetrating abutment configured to interface with the fixture
and to permit the abutment to be removably attached to the fixture
to form a fixture-abutment assembly, wherein at least one
anti-microbial surface forms one or more surfaces of the formed
fixture-abutment assembly located in an interior of the formed
fixture-abutment assembly when the fixture is removably attached to
the abutment with an abutment screw, the interior being
substantially isolated from a surrounding environment of the
fixture-abutment assembly.
2. The percutaneous bone conduction implant of claim 1, wherein the
fixture-abutment assembly includes an abutment screw, and wherein
the at least one anti-microbial surface is located on the abutment
screw.
3. The percutaneous bone conduction implant of claim 1, wherein the
abutment has a substantially conical surface, located on the
exterior of the abutment relative to the abutment, with a tapered
exterior contour dimensioned to fit within a tapered interior
contoured surface of a cavity of the fixture to provide a
mechanically tight fit when the abutment is removably attached to
the fixture, wherein the at least one anti-microbial surface is
located at the interface of the conical exterior of the abutment
and the tapered interior contoured face of the fixture.
4. The percutaneous bone conduction implant of claim 1, wherein a
first part of the fixture located opposite screw threads of the
fixture and a first part of the abutment located adjacent to the
first part of the fixture interface with each other with a conical
fit when the abutment is removably attached to the fixture to form
the fixture-abutment assembly, wherein the at least one
anti-microbial surface is located at the interface of the first
parts.
5. The percutaneous bone conduction implant of claim 1, wherein the
interior of the formed fixture-abutment assembly is a closed
environment hermetically isolated from an external environment of
the formed fixture-abutment assembly.
6. The percutaneous bone conduction implant of claim 1, wherein the
at least one anti-microbial surface is substantially isolated from
an external environment of the formed fixture-abutment assembly
such that the anti-microbial coating does not elute anti-microbial
substances when there is a tight seal between the interior of the
formed fixture-abutment assembly and the exterior of the formed
fixture-abutment assembly.
7. The percutaneous bone conduction implant of claim 1, wherein the
at least one anti-microbial surface is anti-microbially activated
only when exposed to moisture, and wherein the interior of the
formed fixture-abutment assembly is substantially isolated from an
external environment of the formed fixture-abutment assembly such
that the at least one anti-microbial surface in the interior is not
exposed to moisture and therefore is not anti-microbially
activated.
8. The percutaneous bone conduction implant of claim 1, wherein the
at least one anti-microbial surface comprises silver.
9. The percutaneous bone conduction implant of to claim 1, wherein
the at least one anti-microbial surface is contained in a reservoir
in the fixture-abutment assembly.
10. The percutaneous bone conduction implant of to claim 2, wherein
the abutment screw is made substantially of an anti-microbial
material.
11. The percutaneous bone conduction implant of claim 10, wherein
the abutment screw is made substantially of silver or a silver
alloy.
12. A percutaneous bone conduction implant, comprising: a fixture
configured to be anchored in the recipient's skull; and a
skin-penetrating abutment configured to interface with the fixture
and to permit the abutment to be removably attached to the fixture
to form a fixture-abutment assembly, wherein the abutment includes
a first coupling portion adapted to receive a second coupling
portion of a bone conduction device and to establish a mechanical
connection with the bone conduction device, and wherein at least
one anti-microbial surface is present in the formed
fixture-abutment assembly and located in an interior of the formed
fixture-abutment assembly when the fixture is removably attached to
the abutment with an abutment screw, the interior being
substantially isolated from a surrounding environment of the
fixture-abutment assembly.
13. The percutaneous bone conduction implant of claim 12, wherein
the at least one anti-microbial surface is configured to kill at
least 99% of all bacteria by quantity that come into contact with
the at least one anti-microbial surface.
14. The percutaneous bone conduction implant of claim 12, wherein
the at least one anti-microbial surface is located on surfaces that
are at least one of on or adjacent to an abutment screw configured
to screw into the fixture to releasably attach the abutment to the
fixture, wherein the friction coefficient of the least one
anti-microbial surface is about the same as the friction
coefficient which would be present at the same surfaces without the
at least one anti-microbial surface.
15. The percutaneous bone conduction implant of claim 12, the
friction coefficient of the surfaces with the at least one
anti-microbial surface is the same as the friction coefficient
which would be present at the same surfaces without the at least
one anti-microbial surface.
16. The percutaneous bone conduction implant of claim 12, wherein
the at least one anti-microbial surface is a silver-based
anti-microbial surface that kills Staph and Epidermidis and
Methicillin resistant Staph Aureus (MRSA).
17. A percutaneous bone conduction implant, comprising: a fixture
configured to be anchored in the skull of the recipient; and a
skin-penetrating abutment configured to interface with the fixture
and to permit the abutment to be removably attached to the fixture
to form a fixture-abutment assembly through which controlled
vibrations can be directly transmitted from outside the recipient's
body directly into the fixture-abutment assembly, wherein the
abutment is dimensioned to extend from the fixture to above an
outer skin layer of the recipient when the fixture-abutment is
located at a first body location located approximately adjacent a
recipient's pinna and the fixture is anchored in the recipient's
skull.
18. The percutaneous bone conduction implant of claim 17, further
including an abutment screw adapted to extend through the abutment
and screw into the fixture to removably attach the abutment to the
fixture, wherein when the abutment screw is screwed into the
fixture so that the abutment sealingly interfaces with the fixture
to form the fixture-abutment assembly, a micro-leakage pathway is
present, wherein the fixture-abutment is located at the first body
location, extending from outside the recipient to a region between
facing surfaces of the abutment screw and the abutment to at least
one of (i) a region between facing surfaces of the abutment screw
and the fixture and (ii) a region between facing surfaces of the
abutment and the fixture, wherein the at least one anti-microbial
surface is located within the micro-leakage pathway.
19. An implanted percutaneous bone conduction implant, comprising:
a fixture-abutment assembly implanted in the recipient's skull at a
first body location, wherein the fixture-abutment assembly
includes: a fixture anchored in the recipient's skull; and a
skin-penetrating abutment releasably attached to the fixture
extending from beneath a surface layer of an epidermis of the
recipient to an exterior of the recipient above the surface layer
of the epidermis of the recipient at the first body location,
wherein one or more anti-microbial surfaces are present on the
fixture-abutment, the one or more surfaces being located in an
interior of the formed fixture-abutment assembly when the fixture
is removably attached to the abutment, the interior being
substantially isolated from a surrounding environment of the
fixture-abutment assembly.
20. The percutaneous bone conduction implant of claim 19, wherein
the first location is located approximately behind a pinna of the
human body.
21. The percutaneous bone conduction implant of claim 19, wherein
the least one anti-microbial surface is anti-microbially activated
only when exposed to moisture, and wherein the interior of the
formed fixture-abutment assembly is substantially isolated from an
external environment of the formed fixture-abutment assembly such
that the at least one anti-microbial surface in the interior is not
exposed to moisture and therefore is no anti-microbially
activated.
22. A method of implanting a percutaneous bone conduction implant,
comprising: anchoring a fixture in a recipient's skull; and
releasably attaching a skin-penetrating abutment to the fixture to
form a fixture-abutment assembly, wherein the action of releasably
attaching the skin-penetrating abutment to the fixture includes
establishing a hermetically sealed interior in the formed
fixture-abutment assembly, wherein at least one anti-microbial
surface is present on an interior of the formed fixture-abutment
assembly, the interior initially being hermetically sealed from an
exterior of the formed fixture-abutment assembly, and wherein,
after a period of time after releasably attaching the
skin-penetrating abutment to the fixture, the interior ceases to be
hermetically sealed from the exterior of the formed
fixture-abutment assembly while the skin-penetrating abutment is
still releasably attached to the fixture.
23. The method of claim 22, wherein the period of time is over
about one year.
24. The method of claim 23, wherein after the period of time, the
at least one anti-microbial surface has about the same efficacy
with respect to killing microbes as possessed by the surface when
the abutment was releasably attached to the fixture.
25. The method of claim 22, wherein the anti-microbial surface is
silver-based, the method further comprising avoiding exposure of
the at least one anti-microbial surface to at least one of proteins
and acids.
26. The percutaneous bone conduction implant of claim 1, wherein
the at least one anti-microbial surface comprises an anti-microbial
coating, and wherein the anti-microbial coating has a first
thickness corresponding to a first estimated efficacy achieved
during exposure to an environment substantially devoid of proteins
and acids, and wherein the first thickness is substantially less
than a second thickness of an anti-microbial coating corresponding
to a second estimated efficacy achieved during exposure to least
one of proteins and acids, wherein the first estimated efficiency
is about the same as the second estimated efficacy.
27. A percutaneous bone conduction implant, comprising: a fixture
configured to be anchored in a recipient's skull; and a
skin-penetrating abutment configured to interface with the fixture
and to permit the abutment to be removably attached to the fixture
to form an fixture-abutment assembly through which controlled
vibrations can be directly transmitted from outside the recipient's
body directly into the fixture-abutment assembly, wherein the
formed fixture-abutment assembly includes one or more surfaces
located in an interior of the formed fixture-abutment assembly when
the fixture is removably attached to the abutment with an abutment
screw, the interior being substantially isolated from a surrounding
environment of the fixture-abutment assembly, and wherein at least
one of the one or more surfaces are at least one of anti-adhesive,
bacterial repellant or coated with an antibiotic agent.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims foreign priority to German
Patent Application No. 102009014771.3, entitled "Hearing Aid
Implant," filed on 25 Mar. 2009, which is hereby incorporated
herein by reference herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates generally to hearing
prosthesis and, more particularly, to a percutaneous bone
conduction implant.
[0004] 2. Related Art
[0005] For persons who cannot benefit from traditional acoustic
hearing aids, there are other types of commercially available
hearing prostheses such as, for example, bone conduction hearing
prostheses (also referred to as "bone conduction hearing aids," and
"bone conduction devices;" "bone conduction devices" herein). Bone
conduction devices mechanically transmit sound information to a
person's inner ear by transferring vibrations to person's skull.
This enables the hearing prosthesis to be effective regardless of
whether there is disease or damage in the middle ear.
[0006] Traditionally, bone conduction devices transfer vibrations
from an external vibrator to the skull through a bone fixture that
penetrates the skin and is physically attached to both the vibrator
and the skull. Typically, the external vibrator is connected to the
percutaneous bone conduction implant located behind the external
ear so that sound is transmitted via the skull to the cochlea.
Generally, the percutaneous bone conduction implant connecting the
bone conduction device (the portion containing the vibrator) to the
skull generally comprises two components: a bone attachment piece
(e.g., bone fixture/fixture) that is attached or implanted directly
into the skull, and a skin penetrating piece attached to the bone
attachment piece (often referred to as an abutment).
SUMMARY
[0007] According to one embodiment of the present invention, there
is a percutaneous bone conduction implant that includes a fixture
configured to be anchored in the recipient's skull. The
percutaneous bone conduction implant further includes a
skin-penetrating abutment configured to interface with the fixture
and to permit the abutment to be removably attached to the fixture
to form a fixture-abutment assembly. In an embodiment, at least one
anti-microbial surface forms one or more surfaces of the formed
fixture-abutment assembly located in an interior of the formed
fixture-abutment assembly when the fixture is removably attached to
the abutment with an abutment screw. In this embodiment, the
interior is substantially isolated from a surrounding environment
of the fixture-abutment assembly.
[0008] According to another embodiment of the present invention,
there is a percutaneous bone conduction implant, comprising a
fixture configured to be anchored in the recipient's skull. The
implant further comprises a skin-penetrating abutment configured to
interface with the fixture and to permit the abutment to be
removably attached to the fixture to form a fixture-abutment
assembly. In an embodiment, the abutment includes a first coupling
portion adapted to receive a second coupling portion of a bone
conduction device and to establish a mechanical connection with the
bone conduction device. Further, at least one anti-microbial
surface is present in the formed fixture-abutment assembly and
located in an interior of the formed fixture-abutment assembly when
the fixture is removably attached to the abutment with an abutment
screw, the interior being substantially isolated from a surrounding
environment of the fixture-abutment assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the present invention are described herein
with reference to the attached drawing sheets in which:
[0010] FIG. 1 is a cross-sectional view of a percutaneous bone
conduction implant provided with an anti-microbial coating, in
accordance with embodiments of the present invention;
[0011] FIG. 2 is a cross-sectional view of another percutaneous
bone conduction implant provided with an anti-microbial coating, in
accordance with embodiments of the present invention;
[0012] FIG. 3 is cross-sectional side view of the percutaneous bone
conduction implant of FIG. 2 illustrating an exaggerated possible
micro-leakage path and an exaggerated anti-microbial coating;
and
[0013] FIG. 4 is a planar partial view of a proximate end of a
fixture, illustrating the tapered connection between the fixture
and the abutments of the percutaneous bone conduction implant
illustrated in FIG. 2.
DETAILED DESCRIPTION
[0014] In an embodiment, there is a percutaneous bone conduction
implant for anchorage of a bone conduction device to a recipient's
skull. The percutaneous bone conduction implant includes a fixture
configured to be implanted in the recipient's skull, and a
skin-penetrating abutment configured to detachably interface with
the fixture to form a fixture-abutment assembly. Controlled
vibrations generated by the bone conduction device may be
transmitted from outside the recipient's body directly into the
fixture-abutment assembly, and into a recipient's skull. In an
embodiment, at least one anti-microbial surface forms one or more
surfaces of the formed fixture-abutment assembly. The
anti-microbial surface may be located in an interior of the formed
fixture-abutment assembly when the fixture is removably attached to
the abutment, the interior being substantially isolated from a
surrounding environment of the percutaneous bone conduction
implant.
[0015] More particularly, aspects and exemplary embodiments
disclosed herein are generally directed to a percutaneous bone
conduction implant in which the surfaces of a fixture
(corresponding to a bone attachment piece) and an associated
abutment (corresponding to a skin penetrating piece) are provided
with an anti-microbial coating configured to reduce and/or
eliminate undesirable micro-leakage of bacteria (hereinafter
"micro-leakage) which may be caused, by way of example only and not
by way of limitation, by gaps between mating surfaces of the
fixture, the abutment, and/or the abutment screw. These gaps may be
present due to imperfections in the mating surfaces, deficiencies
in the tightening torques provided to the abutment screw (e.g.
failure to properly initially implant the percutaneous bone
conduction implant), misalignment of the abutment with the fixture
component, etc. (e.g. where a gap was present beginning at
implantation of the implant), These gaps may also be present as an
intractable feature resulting from use and/or age of a percutaneous
bone conduction implant (e.g. the gap may initially not be present
in the percutaneous bone conduction implant, but, after a number of
years of use, a gap is opened creating a micro-leakage path).
[0016] In certain embodiments, the percutaneous bone conduction
implant has a smooth outer contour facing the surrounding soft
tissue of the skin to minimize unwanted pockets or gaps in the
tissue-device interface. In some embodiments, the regions of the
fixture and the abutment which mate with each other have inverse
conically-shaped regions such that, when mated, the fixture forms
the bottom of an hourglass shape while the abutment forms the top
of the hourglass shape. In other embodiments, the regions of the
fixture and the abutment which mate with each other have respective
mating surfaces that extend at right-angles to each other. In some
embodiments, the fixture forms the bottom leg of a "Y" shape and
the abutment forms the top legs of the "Y" shape. In an embodiment,
dimensions of the hourglass shape configuration and the "Y" shaped
configuration are such that the recipient's skin abuts the narrow
region of the hourglass configuration and the intersection of the
legs of the "Y" shape configuration, respectively.
[0017] In certain embodiments, the upper end face of the fixture
has an open cavity with a tapered interior surface forming a seat
for the tapered exterior side wall of the abutment. In other
embodiments, the bottom end face of the abutment has an open cavity
with a cylindrical interior surface forming a female seat for a
cylindrical exterior male portion of the fixture. These
configurations may create a good connecting fit between the fixture
and abutment so as to reduce the risk of micro-leakage.
[0018] Percutaneous bone conduction implants suffer from risks of
infection and inflammation at the skin-implant interface resulting
from bacterial colonization in the area around the interface. An
embodiment of the percutaneous bone conduction implant disclosed
herein increases the integration of the skin to the percutaneous
bone conduction implant thereby decreasing the likelihood that a
gap will form between the two. Such gaps are, unfortunately, an
ideal environment for the bacteria. By creating an integration of
the skin to the percutaneous bone conduction implant the adverse
skin reactions associated with bone anchored percutaneous bone
conduction implants may be reduced.
[0019] Integration between the skin and the implant occurs when the
soft tissue encapsulates the implant in fibrous tissue and does not
readily dissociate itself from the implant. U.S. Provisional Patent
Application No. 60/951,163, entitled "Bone Anchor Fixture for a
Medical Prosthesis," filed Jul. 20, 2007, discloses a surface
modification which reduces certain adverse skin reactions, and
which may be implemented in embodiments of the present invention.
The contents of U.S. Provisional Patent Application No. 60/951,163
in general, and the surface modification disclosed therein in
particular, is hereby incorporated by reference for application to
some embodiments disclosed herein, conceptually and/or exactly, to
reduce and/or eliminate adverse skin reactions associated with bone
anchored percutaneous bone conduction implants. In other
embodiments the abutment is coated to reduce the shear modulus, as
described in greater detail below.
[0020] Embodiments of the percutaneous bone conduction implant may
be used in connection with systems where sound is transmitted via
the skull directly to the inner ear of a person with impaired
hearing. However, embodiments of the percutaneous bone conduction
implant may also be configured for use in connection with other
types of systems with components anchored in the skull and for ear
or orbital prostheses which are also anchored in the skull. Other
applications of the percutaneous bone conduction implant are also
contemplated.
[0021] FIGS. 1-3 depict a cross-sectional view of a bone anchored
percutaneous bone conduction implant 100 according to exemplary
embodiments of the present invention. Percutaneous bone conduction
implant 100 is illustrated in FIGS. 1-3 with a screw-shaped fixture
1 and a skin-penetrating abutment 2. These two components are
connected by an elongate coupling shaft or an abutment screw 3
having, in one embodiment, a cylindrical screw head 40. Screw head
40 has an internal hex or multi-lobular configuration for a
cooperating insertion tool (not illustrated here). In an alternate
embodiment, screw head 40 may instead or in addition to the
internal hex head utilize an external hex geometry.
[0022] Fixture 1 may be made of any material that has a known
ability to integrate into surrounding bone tissue (i.e., it is made
of a material that exhibits acceptable osseointegration
characteristics). (This may also be the case with respect to the
abutment 2, in some embodiments.) In one embodiment, fixture 1
includes a main body 4. In an embodiment, the fixture 1 is made of
titanium. Fixture 1 has a main body 4 with an outer screw thread 5
which is configured to be installed into the skull. Fixture 1 also
comprises a flange 6 configured to function as a stop when fixture
1 is installed into the skull. Flange 6 prevents the screw thread 5
from completely penetrating through the skull. Fixture 1 may
further comprise a tool-engaging socket having an internal grip
section for easy lifting and handling of fixture 1. Tool-engaging
socket and the internal grip section are described and illustrated
in U.S. Provisional Application No. 60/951,163, entitled "Bone
Anchor Fixture for a Medical Prosthesis," filed Jul. 20, 2007, the
contents of which is hereby incorporated by reference herein for
application, exactly and/or conceptually, to installing and
manipulating the fixture 1.
[0023] The main body 4 of fixture 1 may have length sufficient to
securely anchor the fixture 1 into the skull without penetrating
entirely through the skull. The length of the main body 4 may
therefore depend on the thickness of the skull at the implantation
site. In one embodiment, the main body of the fixture 1 has a
length that is no greater than 5 mm, measured from the planar
bottom surface 8 of the flange 6 to the end of the distal region 1B
(this limits and/or prevents the possibility that the main body 4
might go completely through the skull). In another embodiment, the
length of the main body is from about 3.0 mm to about 5.0 mm.
[0024] In the embodiment depicted in FIG. 1, the main body of
fixture 1 has cylindrical proximate end 1A, a straight, generally
cylindrical body, and a screw thread 5. The distal region 1B of
fixture 1 may be fitted with self-tapping cutting edges formed into
the exterior surface of the fixture. Further details of the
self-tapping features are described in International Patent
Application WO 02/09622, the contents of which is hereby
incorporated by reference herein for application, exactly and/or
conceptually, to configuring fixture 1 to be installed into a
skull.
[0025] In the embodiment depicted in FIGS. 2-3, the main body of
the fixture 1 has a tapered apical proximate end 1A, a straight,
generally cylindrical body, and a screw thread 5. The distal region
1B of fixture 1 may also be fitted with self-tapping cutting edges
(e.g., three edges) formed into the exterior surface of the
fixture.
[0026] A clearance or relief surface may be provided adjacent to
the self-tapping cutting edges in accordance with the teachings of
U.S. Patent Application Publication No. 2009/0082817, the contents
of which is hereby incorporated by reference herein for application
to configuring fixture 1 to be installed into a skull. Such a
design may reduce the squeezing effect between the fixture 1 and
the bone during installation of the screw by creating more volume
for the cut-off bone chips.
[0027] As illustrated in FIGS. 1-3, flange 6 has a planar bottom
surface for resting against the outer bone surface, when anchoring
fixture 1 has been screwed down into the skull. Again, flange 6
prevents the fixture 1 from completely penetrating through the
skull. Preferably, flange 6 has a diameter which exceeds the peak
diameter of the screw threads 5 (the screw threads 5 of the fixture
1 may have an outer diameter of about 3.5-5.0 mm). In one
embodiment, the diameter of the flange 6 exceeds the peak diameter
of the screw threads 5 by approximately 10-20%. Although flange 6
is illustrated in FIGS. 1-3 as being circumferential, flange 6 may
be configured in a variety of shapes so long as flange 6 has a
diameter or width that is greater than the peak diameter of the
screw threads 6. Also, the size of flange 6 may vary depending on
the particular application for which the percutaneous bone
conduction implant 100 is intended.
[0028] In FIGS. 2-3, the outer peripheral surface of flange 6 has a
cylindrical part 120 and a flared top portion 130. The upper end of
flange 6 is designed with an open cavity having a tapered inner
side wall 17. The tapered inner side wall 17 is adjacent to the
grip section (not shown). The interior of the flange 6 further
includes an inner bottom bore 150 having internal screw threads for
securing a coupling shaft of abutment screw 3.
[0029] In FIG. 1, the upper end 1A of fixture 6 is designed with a
cylindrical boss 140 having a coaxial outer side wall 170 extending
at a right angle from a planar surface 180 at the top of flange
6.
[0030] In one embodiment, increased stability to the attachment
between fixture 1 and abutment 2 is provided as detailed in U.S.
Patent Application Publication No. 2009/0082817, the contents of
which is hereby incorporated by reference herein for application,
conceptually and/or exactly, to providing increased stability to
the attachment of the fixture and the abutment implemented in
embodiments described herein.
[0031] In the embodiments illustrated in FIGS. 2 and 3, the flange
6 has a smooth, open upper end and does not have a protruding hex.
The smooth upper end of the flange 6 and the absence of any sharp
corners provides for improved soft tissue adaptation. Flange 6 also
comprises a cylindrical part 120 which, together with the flared
upper part 130, provides sufficient height in the longitudinal
direction for internal connection with the abutment 2. FIG. 4
illustrates the tapered seat 145 seated within the height 34 of
flange 6 of the percutaneous bone conduction implant 100 depicted
in FIGS. 2 and 3.
[0032] It should be appreciated that the fixture 1, abutment 2 and
coupling shaft 3, may be delivered separately or they may be
delivered in the form of a pre-mounted device as illustrated in WO
2004/105650. In accordance with one embodiment, the percutaneous
bone conduction implant 100 is delivered to the surgeon pre-mounted
in its package to facilitate installation of the entire device in a
single step. Abutment 2 may be pre-mounted to the fixture 1 at the
manufacturing site with the correct tightening torque to obviate
the need for the surgeon to know the correct tightening torque or
to handle the separate pieces of the percutaneous bone conduction
implant 100.
[0033] In contrast to traditional implants which require an outer
fixture hex for tool engagement, the percutaneous bone conduction
implant 100 may be installed by using the recesses 190 in the
abutment 2. These recesses 190 are located on the upper part of the
percutaneous bone conduction implant 100 and are more visible than
a traditional outer hex.
[0034] According to the embodiment shown in FIGS. 2-3, the abutment
2 has a substantially curved, conical outer surface with an upper
edge 10 and a bottom, fixture-connecting part 17B. The upper edge
10 may have a width or diameter that is larger than that of the
bottom, fixture connecting part 17B. The bottom part 17B of the
outer surface has a contour 16 adapted to be seated with the
tapered inner contour 145 of the fixture 1 to create a good
connecting fit between the fixture 1 and abutment 2. The two
conical shaped surfaces not only provides an axially well-defined
fit when assembled together, they also provides for easy
disassembly.
[0035] In some embodiments, designing the upper part of the fixture
1 and the lower part of the abutment 2 with a conical fit reduces
the risk for gaps and unwanted micro-leakage, regardless of any
imperfections in the contact surfaces or incorrect tightening
torques.
[0036] In some embodiments, the abutment 2 is provided with an
inner annular flange 9 adjacent upper edge 10 adapted to cooperate
with second coupling parts (not shown) of an exterior vibrator
(relative to the recipient) through a snap-in action or the like.
Attachment of the second coupling parts of the exterior vibrator
permits vibration to be directly sent from the vibrator into the
percutaneous bone conduction implant/percutaneous bone conduction
implant 100.
[0037] As shown in FIG. 4, the tapered portion 200 of the abutment
2 is characterized by a cone angle 32. The cone angle 32 is
configured so as to securely couple the fixture 1 and the abutment
2 without significant gaps. Preferably, the cone angles 32 and 33
are in the range of about 30.degree. to about 40.degree., with
little or no difference between the cone angles 32 and 33. In one
embodiment, the cone angles 32 and 33 are substantially the same.
In another embodiment, the difference between the cone angles 32
and 33 is about 1.degree. to about 5.degree., and more preferably
about 1.degree..
[0038] In some embodiments, the reduction of the risk of infections
and inflammation that results from bacterial colonization in the
unwanted pockets and gaps that are formed between the skin and the
implant is addressed. As illustrated in FIG. 3, an hourglass waist
angle 38 is generally defined between the exterior peripheral
surface 36 of flared portion 13 of flange 6 and the tapered lower
portion 16 of abutment 2. The hourglass waist angle 38 provides a
smooth outer contour to the facing soft tissue such that unwanted
pockets and gaps are not formed between the surrounding tissue and
the percutaneous bone conduction implant 30. This smooth contour
facilitates integration between the percutaneous bone conduction
implant 30 and the surrounding tissue to substantially eliminate
gaps and unwanted pockets where bacteria might grow. This is in
contrast to many traditional implant devices in which a
comparatively sharp interface is formed with the contacting tissue.
The embodiment depicted in FIG. 2 show an hourglass waist angle is
greater than 90.degree..
[0039] In certain embodiments, the skin-contacting surface of
abutment 2 may be modified in such a way that the shear modulus of
the skin-contacting part of abutment 2 is reduced to less than 35
GPa. The surface of the skin-contacting part of the percutaneous
bone conduction implant abutment 2 may be coated with a
biocompatible polymer or a ceramic material. In accordance with one
aspect of the embodiments, the coating has a thickness of
approximately 0.001-50.0 .mu.m. A surface increasing treatment may
be provided resulting in a roughness value S.sub.a of 0.5-10 .mu.m
in place of or in addition to the coating. These modifications to
the skin-contact surface generally reduce the shear modulus and
certain adverse skin reactions. Surface modifications of this type
are discussed in more detail in the co-pending patent application
incorporated by reference elsewhere herein.
[0040] In certain embodiments, the abutment is coated with a
material to reduce the shear modulus. Such a material may be, for
example, a biocompatible polymer, a ceramic material, and/or a
combination thereof. In one specific embodiment, the material has a
thickness of about 0.001 .mu.m to about 50.0 .mu.m. In the same or
other embodiments, the shear modulus is reduced to less than 35
GPa. In the same or other embodiments, the abutment is coated with
a surface increasing material. Such a material may be such that it
provides a roughness value of about 0.5 .mu.m to about 10 .mu.m.
Further details of the above and other features may be found in
Swedish Patent Application No. 0701244-6, which is hereby
incorporated by reference herein.
[0041] The percutaneous bone conduction implant 100 may also be
designed in such a way that it is easy to handle together with
instruments and components used for installation and control of the
implant device. As noted, surgical techniques normally used for
installing the implants have been carried out as a two-step
procedure. In the first step the implant is inserted and maintained
unloaded during a healing period of about a couple of months.
During this healing period it is important to avoid micro-leakage
from the percutaneous bone conduction implant and bacteria
colonization.
[0042] As detailed above, abutment screw 3 is utilized to connect
abutment 2 to fixture 1 to form a mechanically tight seal between
the abutment 2 and the fixture 1, to limit and/or eliminate
micro-leakage in the percutaneous bone conduction implant 100.
Unfortunately, sometimes a micro-leakage path is still preset, such
as micro-leakage path 110, as exemplary depicted in FIG. 3. In an
embodiment, anti-microbial agents are applied to one or more
surfaces of the abutment 2, the fixture 1 and/or the abutment screw
3, as will now be described. By applying anti-microbial agents to
surfaces located in this path, the micro-leakage path 110 can be
blocked vis-a-vis bacteria invading the interior of the
percutaneous bone conduction implant 100. This prevents bacteria
from forming a bacteria reservoir in the interior of the
percutaneous bone conduction implant 100 and/or from reaching the
exterior of the percutaneous bone conduction implant 100 through
the micro-leakage path 110.
[0043] In an embodiment, an anti-microbial coating is applied to
the abutment screw 3 in the form of a silver coating in
concentrations sufficient to kill more than 95%, and in some
embodiments more than 99%, and in some embodiments more than 99.9%,
of all bacterial that may come into contact with the treated
surface.
[0044] Herein, a surface having an anti-microbial coating is an
anti-microbial surface. Further, a component made from an
anti-microbial material has an anti-microbial surface if the
anti-microbial material is present in sufficient quantity to have
anti-microbial features.
[0045] In an embodiment, the anti-microbial coating effectively
stops microbes from multiplying and migrating/advancing through the
interior of the percutaneous bone conduction implant 100 to the
exterior of the percutaneous bone conduction implant 100 through
the micro-leakage path 110, thus reducing the number of skin
complications associated with implants having the configuration as
described herein. Because bacteria tend to live on the surface of a
structure, coating interior surfaces of the percutaneous bone
conduction implant 100 is an effective approach to
reducing/preventing bacterial advancement through the micro-leakage
path 110.
[0046] In an embodiment, this provides a failsafe feature in the
event that the abutment screw 3 loosens (thus opening a gap through
which microbes may advance) during the time that the percutaneous
bone conduction implant 100 is implanted in a skull. Such loosening
may occur when the surgeon fails to apply sufficient torque to the
abutment screw 3.
[0047] Referring to FIGS. 1-3, when fixture 1, abutment 2 and
abutment screw 3 are properly mounted together, the interior parts
12 and 13 in the fixture 1 and the abutment 2, respectively are
closed inside the percutaneous bone conduction implant 100 and do
not face/are not exposed to any surrounding tissue or surrounding
atmosphere (i.e., the environment surrounding the percutaneous bone
conduction implant 100). Also, during normal implantation, the
surface 14 of the abutment screw 3 below the screw head 15 is
closed within the implant assembly. In some embodiments, the
interior parts are initially hermetically sealed from the exterior
environment of the implant assembly, at least until a micro-leakage
path is opened.
[0048] According to an embodiment, in addition to the mechanically
tight fit obtained by the interface of the abutment 2 with the
fixture 1 when the abutment screw 3 releasably secures the abutment
2 to the fixture 1 to form a fixture-abutment assembly, an
anti-microbial coating is present on surfaces of interior part 13
of the abutment 2 and/or on surfaces of interior part 12 of the
fixture 1 and/or on surfaces of part 14 of the abutment screw 3.
The interior parts 13 and 12 are those parts of the abutment and
fixture that do not face/are not exposed to the tissue or
surrounding atmosphere when the components of the percutaneous bone
conduction implant 100 are properly mounted. When properly mounted,
the environment in the interior of the percutaneous bone conduction
implant 100 is closed from the outside of the percutaneous bone
conduction implant 100 and thus will remain relatively dry, and
elution of any substances contained in the interior is therefore
limited. In such instances, it is noted that there is no need for
an anti-microbial coating applied to the open interior of the
percutaneous bone conduction implant 100 such as, for example, the
upper edge 10 of the abutment 2.
[0049] By limiting the application of the anti-microbial coating to
interior surfaces in some embodiments, and thus generally shielding
the soft tissue from exposure to the anti-microbial coating at
least until necessary, the general risk inherent in using
anti-microbial treatments--that the microbes develop a resistance
to the treatment--is reduced. Also, silver contact with the bone
may have a deleterious effect on the bone. Sliver contact with the
bone is reduced by limiting the coating to the interior of the
percutaneous bone conduction implant 100. Further, by containing
the silver based anti-microbial coating to the interior of the
percutaneous bone conduction implant 100, negative effects on the
soft tissue may be reduced as well (e.g., silver sometimes
discolors skin).
[0050] FIG. 3 depicts an exemplary embodiment where an
anti-microbial coating 115 is applied to surfaces of the abutment
screw 3. (Note that element 115 is only depicted in FIG. 3 as being
present on one side of the abutment screw 3, this for convenience
of depicting the hypothetical micro-leakage path 110--in practice,
the coating 115 could be present all the way around the abutment
screw 3, at least in the areas of the screw 3 opposite the abutment
2 (e.g., in the area of interior part 13)).
[0051] In one embodiment, the anti-microbial agent used to form the
coating is a substance which is tightly bound to the respective
surfaces of the percutaneous bone conduction implant 100 and does
not leach out to the tissue. In an embodiment, the anti-microbial
effect is confined to the respective surface or surface interface
and thus need not be a dose dependent drug elution.
[0052] In one embodiment, the anti-microbial coating comprises a
surface bound silver or silver containing compound. Silver is
considered safe and is used in several medical device applications,
such as by way of example only and not by way of limitation, wound
dressings and catheters. However, there are several other elemental
substances that might have a similar effect including iodine, which
is a common antiseptic agent. Some embodiments may thus utilize an
iodine-based anti-microbial coating.
[0053] According to an embodiment, silver is dispersed as small
particles to increase the total surface area of the silver compound
of the anti-microbial coating. In another embodiment, the silver is
dispersed in a carrier (e.g., made of a polymer, a hydrogel, a
ceramic or the like), from which the silver is permitted to slowly
erode if the sliver comes into contact with a fluid due to a breach
in the mechanically tight seal established in the percutaneous bone
conduction implant 100.
[0054] In one embodiment the silver is ion-sputtered, vacuum
deposited and/or powder coated onto the abutment screw 3, the
fixture 1 and/or the abutment 2. In yet another embodiment, the
abutment screw 3 and/or other components of the percutaneous bone
conduction implant 100 could be made out of silver or a silver
alloy, providing that a sufficiently anti-microbial effect may be
obtained.
[0055] In some embodiments, an adsorption process may be utilized
to apply some anti-microbial coatings to the components of the
percutaneous bone conduction implant 100 (e.g., the parts that are
to be coated are put in a liquid containing the antimicrobial
agent).
[0056] An embodiment provides a long term sustained anti-microbial
effect relative to other coatings/coatings applied in other
fashions/coatings that are permitted to be exposed to different
environments. That is, in embodiments where the anti-microbial
coating is substantially isolated from an external environment of
percutaneous bone conduction implant 100 (as described in
embodiments herein) such that the anti-microbial coating does not
elute anti-microbial substances when there is a tight seal between
the interior of the percutaneous bone conduction implant and the
exterior of the percutaneous bone conduction implant, the
anti-microbial coating remains substantially intact. The coating
thus exhibits about the same potency/efficacy as possessed by the
coating when the percutaneous bone conduction implant was first
implanted in the skull of the recipient. This is because the tight
seal of the implants described herein prevents initial/continued
moisture intrusion into the interior of the percutaneous bone
conduction implant 100. Thus, when a functionally tight seal is
present, the coating does not elute anti-microbial material/elutes
minimal amounts of anti-microbial material. However, in time
(months, and/or years), if the abutment screw 3 becomes loose, or a
gap opens permitting the interior of the coupling to be exposed to
the exterior environment for any other reason, thereby creating a
micro-leakage path, at that time, the anti-microbial coating is
about as "new" (e.g., has about the same potency/efficacy) as it
was when the percutaneous bone conduction implant 100 was first
implanted, and is activated with about the full potency (again,
even months and years after initial implantation). This starkly
contrasts with application of the anti-microbial coating to
components that are frequently exposed/initially exposed/quickly
exposed to moisture, in which case the anti-microbial coating
begins to elute and the potency of the anti-microbial coating is
relatively quickly reduced.
[0057] In the same vein, embodiments include percutaneous bone
conduction implants 100 where only trace amounts (nanograms) of
silver or other anti-microbial agent can leak out to the soft
tissue, thus providing utility to people who are allergic to
silver. This also reduces the likelihood that the silver will
discolor the skin. By way of comparison, the silver utilized in
some embodiments is less than 300 times the silver used in would
dressings. In wound dressings, most of the silver is released into
the body within a week (as compared to an approximately 6 month
period for the silver to leak into soft tissue from the
percutaneous bone conduction implant 100, and this only after the
interior is exposed to moisture due to a gap opening up).
[0058] In some embodiments, anti-microbial coatings utilizing
silver do not have a negative effect on the mechanics of the tight
seal formed by the components of the percutaneous bone conduction
implant 100. For example, the coatings did not significantly (or
even noticeably and/or at all) increase the friction between the
mating components of the percutaneous bone conduction implant 100.
Further, the coating was not damaged when a torque of 30 Ncm was
applied to the abutment screw 3 (about a typical torque applied to
the abutment screw 3 when the abutment 2 is secured to the fixture
1).
[0059] In some embodiments, the silver-based anti-microbial coating
kills Staph and Epidermidis and Methicillin resistant Staph Aureus
(MRSA).
[0060] In some embodiments, the coating is protected from
environments containing proteins, even after a micro-leakage path
is opened exposing the exterior environment to the interior of the
percutaneous bone conduction implant 100. Proteins may tend to
neutralize silver ions in a silver-based anti-microbial coating. If
the coated surfaces are shielded from proteins/the amount of
proteins that are exposed to the coated surfaces is controlled to
be low (such as that compared to exposure to proteins in the mouth
of the recipient) such as by way of example only and not by way of
limitation, location of the percutaneous bone conduction implant
100, the lower the needed concentration of silver is in the
coating/the longer the coating will remain potent. That is, if the
coatings are exposed to proteins, a higher concentration of silver
is needed to obtain the same anti-microbial effect, and thus a
lower concentration may be utilized (relative to a coating that
will be exposed to proteins at levels that may be found, for
example, in the mouth of the recipient).
[0061] In some embodiments, the coating is protected from
environments containing acids, even after a micro-leakage path is
opened exposing the exterior environment to the interior of the
percutaneous bone conduction implant 100. Acids may tend to speed
the elution of silver from the anti-microbial coating. If the
coated surfaces are shielded from acids/the amount of acids that
are exposed to the coated surfaces is controlled to be low (such as
that compared to exposure to acids in the mouth of the recipient),
such as by way of example only and not by way of limitation,
location of the percutaneous bone conduction implant 100, the lower
the needed concentration of silver is in the coating/the longer the
coating will remain potent. That is, if the coatings are exposed to
acids, a higher concentration of silver is needed to obtain the
same anti-microbial effect, and thus a lower concentration may be
utilized (relative to a coating that will be exposed to acids at
levels that may be found, for example, in the mouth of the
recipient).
[0062] By protecting the coating from acids and proteins, a coating
that might otherwise last weeks or months may instead last for
years.
[0063] Various kinds of silver containing compounds can be used in
various embodiments. By way of example only and not by way of
limitation, silver compounds usable in embodiments include
silveroxides, silverperoxides, chlorhexidine-silver sulfadiazines,
silverbromides, silverchlorides and other silverhalides or salts of
silver.
[0064] In yet another embodiment, a zinc or a zinc containing
compound is used. Zinc is believed to have a similar anti-microbial
effect as silver, or at least an adequate anti-microbial effect,
and is also used in wound dressing applications.
[0065] In yet another embodiment, interior surfaces of the
percutaneous bone conduction implant 100 are anti-adhesive and/or
or bacterial repellant. Such may be achieved through the use of
poly-ethylene glycol coated surfaces and fluoropolymer coated
surfaces (Teflon.RTM., etc.) In some embodiments, the surface is
functionalized with a multitude of negatively charged molecules
which repel negatively charged bacteria. Electro-polished surfaces
are also, to some degree, anti-adhesive, and, in some embodiments,
may be used.
[0066] In yet another embodiment, an anti-biotic agent such as
rifampin, tetracycline, cyclosporine, gentamicin, vancomycin,
penicillin or sulfonamide compounds, may be utilized. These
compounds may, in such case, be bound to a drug eluting matrix.
However, the shelf life of a percutaneous bone conduction implant
100 using such compounds may be short, although, in some
applications, sufficiently long to have utility. Anti-biotics are
usually sorted into groups based on their chemical or biochemical
origin. Antibiotic groups that may be used in an anti-bacterial
coating include aminoglycosides, carbapenems, cephalosporines
(1st-5th generation), glycopeptides, macrolides, penicillins,
quinolones, sulfonamides, tetracyclines, etc.
[0067] In one embodiment, anti-microbial/anti-bacterial agents
(which may be any of the above-mentioned agents) are contained in a
reservoir, such as, for example, in the form of small pores or
cavities on the interior surfaces of the percutaneous bone
conduction implant 100.
[0068] Depending on the type of anti-microbial coating applied to
the interior surfaces of the percutaneous bone conduction implant
100, the friction coefficient of those surfaces might be affected.
If the coating increases the friction coefficient, the diameter of
the abutment screw 3 might be reduced (for instance by way of a
"waist" or area of reduced diameter in the mid-section of the
abutment screw 3) to achieve "stretching" of the screw. Such
stretching is useful for maintaining a safe, long-life stable screw
connection. On the other hand, if the coating reduces the friction
coefficient, the abutment screw 3 might be designed with an
increased diameter which strengthens the abutment screw 3.
[0069] It should be understood that in some embodiments, the
methods described above for preventing micro-leakage are based on
the formation of a mechanically tight seal and/or a surface
modification for reducing shear forces and increasing surface area
vis-a-vis the implant. If there is an unwanted gap in the system
due to failure of the tight seal, loosening of a component or the
like (where the gap is formed after implantation), failure to
properly implant the percutaneous bone conduction implant (in which
case a gap may be present at implantation) the above methods
disclosed herein are less effective against micro-leakage.
[0070] Further features and capabilities of a bone conduction
implant (also referred to as a bone conduction hearing aid) may be
found in U.S. Provisional Application No. 60/951,169, entitled
"Percutaneous bone conduction implant For a Bone Anchored Hearing
Device," filed Jul. 20, 2007, U.S. Provisional Application No.
60/951,163, entitled "Bone Anchor Fixture for a Medical
Prosthesis," filed Jul. 20, 2007, and U.S. Patent Application
Publication No. 2009-0082817, entitled "Percutaneous bone
conduction implant for a Bone Anchored Hearing Device," published
on Mar. 26, 2009, which are hereby incorporated by reference herein
for application of their teachings, conceptually and/or exactly, to
the reduction/elimination of micro-leakage paths, and for the
configurations of a percutaneous bone conduction implant disclosed
therein. In this regard, embodiments include application of an
anti-microbial/bacterial coating or other surface treatment as
detailed herein to any interior surface of the components taught in
those applications/publications.
[0071] In another embodiment, the percutaneous bone conduction
implant and/or the bone conduction implant has some or all of the
functionality and/or some or all of the structure disclosed in U.S.
Pat. No. 4,498,461, the contents pertaining to functionality and
structure being incorporated herein by reference.
[0072] In another embodiment, the anti-microbial coatings may be
utilized in conjunction with any of the other
methods/devices/systems disclosed in the above "related art"
section.
[0073] As noted above, this patent application claims foreign
priority to German Patent Application No. 102009014771.3, entitled
"Hearing Aid Implant," filed on 25 Mar. 2009, the entire contents
of that German Patent Application being incorporated by reference
herein.
[0074] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. It will be
apparent to persons skilled in the relevant art that various
changes in form and detail can be made therein without departing
from the spirit and scope of the invention. Thus, the breadth and
scope of the present invention should not be limited by any of the
above-described exemplary embodiments, but should be defined only
in accordance with the following claims and their equivalents. All
patents and publications discussed herein are incorporated in their
entirety by reference thereto.
* * * * *